edit: urgh sorry for the wall of text. I'll understand if you don't read it. It looks horrible and I probably wouldn't read it all if someone else wrote it.
Well I see you and I will agree on some things in regards to Hollywood.
Laura Linney is a phenomenal actress, one of the best of her generation. Would I cast her in a blockbuster - yes. Would Hollywood - yes. She's in some pretty mainstream movies. Why she's not in more is probably up to her. She does a lot of indie movies because they seem to be the good female roles. Basically between her and Streep they get the pick of the lot. She doesn't seem to want the notoriety so why do a big movie when you can do a good movie.
It's not always Hollywood that doesn't want the actor it's the actor that doesn't want Hollywood. I's dare say there's a lot of these so called 'good looking' actresses that would be down right envious of Linney's career and the roles she gets.
Before I get onto your supposed vendetta against George Clooney, may I say this first:
You say blockbuster like it's a good thing.
My point is that the blockbusters today are dominated by 'mimbo's'
To that I say: so what. I don't want Seymour Hoffman and Norton in blockbusters. Why? Because it usually will be a crap movie where they won't get a chance to perform.
An example: Norton and Hulk.
The studio wanted Norton for the Ang Lee Hulk and he said no. Which exemplifies my point that Hollywood in certain circumstances want the 'artsy' actor but that actor doesn't want the role. If Norton did Hulk maybe we as an audience wouldn't have got The 25th Hour (I don't know if they were filming at the exact same time I'm just using it as an example or hypothetical)
It's like choosing fast food over a fine meal. You won't eat the fast food unless there is nothing else around. If you can mostly always choose the fine food, most people certainly would.
Unfortunately Hollywood makes an excess of films. There's only so many good actors around/ available. That's when you start filling the roles with less talented people. If you are going to fill a role with a less talented person that isn't going to impress the audience with their performance well they better be damn pretty to impress them instead. Fortunately or unfortunately there are more pretty people in the world than talented people. And that's Hollywood for you.
And then there's your exceptions like Superman with Brando and Hackman. It's better than the average blockbuster because it doesn't want to just be a blockbuster it wants be a good film and that in turn attracts the right actors. The same with Batman Begins and now The Dark Knight. It wanted to be more than your typical Batman Returns type blockbuster movie and just be a good film, a more cerebral blockbuster and that in turn attracts the talent.
Again I could go on and on but I'm getting lost in my own thoughts as it is. Am I still coherent?
On to Clooney.
Jaws is a bad example because it's such a classic that no one wants to even think about alternate casting and if it was made today. The actors in their roles are such perfection that you can't imagine anyone else.
But to use your example, would it be so bad if Clooney was in such a movie? Do you actual have a vendetta against him?
In case you can't tell I actually like him. But now if you suggested someone like Matthew McConaughey my answer would be different (though he's actually a decent comedic actor he just makes usually terrible movies.)
Clooney actually played a similar role in the Perfect Storm, was he so bad? Ok the movie was.
I also think you are paying too much attention to the Oscars. History deems Paul Newman to be a revered actor not how many Oscars he won. I could think of a dozen examples in as many seconds of actors that have failed to have been recognised by the Academy. There's even as many examples of actors that were awarded Oscars and did not deserve it.
Does Clooney fall into the latter category? You apparently think so, I do not.
Did you see Syrianna? I thought Clooney was very good in the role. I don't think it was his best work (close) nor do I think it was the best supporting role ever to win an Oscar (that would just be silly). But in the year deemed by the Academy as 2005 it was the best supporting role. Clooney's competition was Matt Dillon for Crash, Paul Giamatti for Cinderella Man, Jake Gyllenhaal for Brokeback Mountain and William Hurt for A History of Violence.
So I propose who do you think should have won it? Sometimes the Academy Awards is all about giving the award to someone who is the best at that particular time (sometimes the nominees are filler) and sometimes the Academy gives the award for a body of work (ie Scorsese or Denzel Washington). In the case of Clooney's Oscar it could have been both.
Do I think Clooney = DeNiro? No.
You make a fair point about Harrison and Eastwood. But sometimes they can be truly astonishing in that field, ie Eastwood in Unforgiven.
It would be stupid not to say looks are important in Hollywood, it's a visual medium and looks have always been important. Hell looks are of increasing importance in the real world and even as important in the music industry as it is in Hollywood when it should be about the sound created not the image created.
Oh and on last bit of defence for Clooney he won his Oscar for best supporting actor and Newman won his for Best Actor. Also to tie everything together why did Clooney win his for his least attractive role instead of say Good Night and Good Luck or Michael Clayton? Plain talent maybe :)
Oh I'm going to get drilled for my defence of Clooney. But I'll still stand by defence of people like him and Pitt (who I don't think is Oscar calibre yet - I'll wait for Benjamin Button) and Robert Redford. Same scenario different era.